Generally, a fuel cell vehicle includes a fuel cell stack having a plurality of fuel cells stacked, which are used as a power source thereof, a fuel supplier for supplying hydrogen or the like as a fuel to the fuel cell stack, an air supplier for supplying oxygen as an oxidizing agent necessary for an electrochemical reaction, a water and heat controller for controlling temperature of the fuel cell stack, and so on.
The fuel supplier depressurizes compressed hydrogen in a hydrogen tank to supply it to an anode of the stack as a fuel electrode, and the air supplier activates an air blower to supply air drawn from outside to a cathode of the stack as an air electrode.
When the anode of the stack is supplied with hydrogen, and the cathode is supplied with oxygen, hydrogen ions are separated through a catalytic reaction at the anode. The separated hydrogen ions are delivered to the cathode through an electrolyte membrane, and the electrochemical reaction occurs at the cathode by means of electrons and the hydrogen ions separated at the anode and oxygen, thereby generating electrical energy. More specifically, hydrogen is oxidized electrochemically at the anode, and oxygen is reduced electrochemically at the cathode. The separation movement of the electrons caused as such produces electricity and heat, and a chemical reaction for combining hydrogen and oxygen produces water vapor or water. Though the amount of water produced varies according to states of operation, such as current and operating temperature, it remains inside the fuel cell stack and can be frozen at temperatures below the freezing point.
The frozen water content inside the stack may block a reaction surface or a flow path, thereby hindering a generation of a normal voltage or normal available power output at the next start-up of a vehicle. The more water content is frozen at lower temperature, the generation of the available power output is further deteriorated, which may not allow a fuel cell vehicle to run normally and may cause a time delay in starting.
Though a cold start has been controlled based on temperatures at an inlet and exit of cooling water for a fuel cell, it is impossible to accurately estimate an internal state of a fuel cell when there is a change in the outside temperature between at the time of turning-off and at the restart of a vehicle.
The features described above as the background of the disclosure are only for the understanding of the related techniques of the present disclosure, and such features should not be considered to be fallen within prior art already known to a person skilled in the art to which the disclosure pertains.